P0544

Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1

Indicator

The PCM has detected a malfunction in the exhaust gas temperature sensor circuit.

Code Set Parameters

The exhaust gas temperature sensor utilizes a sensor in the exhaust system to input voltage readings to the PCM. Variations in system voltage that exceed manufacturer’s predetermined limitations will cause a code to be stored and a service engine soon lamp to be illuminated.

Symptoms

There will probably be no obvious codes other than an illuminated service engine soon lamp and a stored trouble code.

Common Causes

Loose, broken, burned, or corroded wiring and/or terminals and connectors are the most common cause of this trouble code bring stored. Other causes may include the exhaust gas temperature sensor being shorted internally (or to ground), a faulty sensor, the presence of an aftermarket off road exhaust system that causes a decrease in back pressure, a severe exhaust leak upstream from the exhaust temperature sensor will also cause this code to be stored.

Common Misdiagnosis

The most common source of mishaps when diagnosing this code comes from mistaken identity. Frequently the oxygen sensor is either mistaken for the exhaust gas temperature sensor or it is believed that the exhaust gas temp sensor is integrated into the heated oxygen sensor. Of course, this is incorrect and replacement of the oxygen sensor/s will not lead to a successful diagnosis.

Diagnosis

The exhaust gas temperature sensor is typically a 2-wire sensor located in the exhaust down pipe, upstream from the catalytic converter (gas engines)

The exhaust gas temperature sensor is used in diesel engines, gasoline burning engines, and even turbocharged engines

In diesel engines, the sensor will likely be located near the diesel particulate filter section of the exhaust system

Turbocharged applications may place the exhaust gas temperature sensor in the exhaust input pipe, near the turbocharger

The exhaust gas temperature sensor is of the temperature reactive resistor variety

The sensor is supplied with a low voltage (usually 5-volts) power wire and a ground wire

As exhaust gas temperature increases, the level of resistance in the sensor decreases, allowing the feedback voltage signal to the PCM to increase

As exhaust temperature decreases (with the engine off), circuit resistance increases and the feedback voltage signal to the PCM decreases

The PCM recognizes these voltage variations as exhaust gas temperature and it reacts accordingly, adjusting ignition timing or the air/fuel ratio in order to lower the exhaust gas temperature and protect the catalytic converter

Several tools will be instrumental in successfully diagnosing this code

A suitable OBD-II scanner (or code reader) and a digital volt/ohmmeter will be most helpful in performing a successful diagnosis

Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data

This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored

Continue by clearing the code and operating the vehicle to see if it returns

This will help to determine whether or not the malfunction is intermittent

After the codes are cleared, test drive the vehicle to see if the code returns

If the code fails to immediately return, you may have an intermittent condition

Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made

Continue your diagnosis with a visual inspection of the exhaust gas temperature sensor and system circuitry

Pay close attention to areas where wiring and connectors are located near hot exhaust components

If all of the exhaust gas temperature sensor circuitry appears to be in proper working order, then proceed with the diagnostic procedure

If certain items appear to be damaged, burned, or corroded, repair or replace them as required, then reset the code and retest the system.
If no burned, damaged, or shorted wiring or loose connectors are detected, disconnect the exhaust gas temperature sensor connector and remove the exhaust gas temperature sensor

Using the digital volt/ohmmeter, check the resistance of the exhaust gas temp sensor

Typical resistance for this sensor should be approximately 150 ohms but double check manufacturer’s specifications prior to testing

Normally, if there is less than 50 ohms of resistance, then you would replace the sensor

If the initial resistance is within specifications, leave the leads of the digital volt/ohmmeter connected and heat the resistor with a heat gun

Carefully observe the resistance level of the sensor (on the screen of the digital volt/ohmmeter) as the temperature is elevated to see if it decreases smoothly

If the resistance level does not decrease with heat and increase as it cools, replace the sensor.
If everything has checked out thus far, turn the key to the “ON” position and test for the presence of a voltage (and a ground signal) at the exhaust gas temperature sensor electrical connector

If there is no low voltage (usually 5-volts) on the signal wire, disconnect the PCM connector and perform a continuity test on the wire using the digital volt/ohmmeter

If there is continuity, the PCM may be faulty (PCM failure is rare and, if replaced, it will need to be reprogrammed)

If no ground is present locate the source and check for continuity using the digital volt/ohmmeter

Repair or replace open or shorted wiring and connectors as required.
Installing high performance exhaust systems (with no catalytic converters) can also cause this code to be set due to the lack of exhaust system back pressure

This condition can be rectified by installing an in line resistor (2.5 ohms) between the signal and ground wires and leaving the exhaust gas temperature sensor disconnected